This invention relates to a belt grinding attachment adapted to be driven by a power tool, electric pneumatic or other, such as a disc or angle grinder.
Australian patent specifications AU-B-74741/81 and 74742/81 disclose a device generally of this type, though primarily adapted for attachment to bench grinders, such device fulfilling the necessary basic functions. Although such devices of the prior art work well, the novel features of the present invention greatly improve its adaptability so as to fit a multitude of power tools from various manufacturers without sacrificing its performance or adding complexity to design.
Devices of this general type include a driven pulley wheel and an idler pulley wheel being generally transversely aligned and parallel and being compressed apart so as to hold and drive an endless abrasive belt wrapped around the two pulley wheels. Of primary importance to good operation of these devices is the accuracy to which the rotational axes of the two pulley wheels are maintained relative to one another. Complicating the necessary structure is the fact that the two rotational axes must be adjustably skewed in order to adjust the correct tracking of each individual belt, and furthermore, they must be biased apart so as to provide necessary tension to the endless belt.
In the prior art these difficult constraints have been successfully met by providing a telescoping structure produced to very precise tolerances and extending between the driven pulley wheel and the idler wheel, see Australian patent publications noted above. The telescoping structure is spring-loaded in compression and adjustably rotated through some relatively small angle about its longitudinal axis at one end proximate the driven wheel. The inner and outer portions of the telescoping section are prevented from rotating relative to one another by a single sandwiched together sliding structure. The rotational adjustment at the driven pulley wheel end is effective to provide the necessary skewing adjustment in order to ensure correct tracking of each individual endless belt.
While this prior art device works perfectly well the necessary high precision of the components do add to the cost of the device. Thus there is room for improvement in providing a cheaper alternative which will not compromise the operational quality of the tool.